Effect of stress on prolactin release in nulliparous and primiparous rats

Reproductive experience modifies seric concentration of prolactin. In adition, stress is known to modulate this neurohormone release. Taken together, these facts are suggestive of a possible interaction. The objective of the present study was to analyze the influence of acute and prolonged stress on prolactin secretion in nulliparous and experienced rats. Wistar nulliparous (n= 12) and primiparous (n= 12) female rats were submitted to a chronic jugular vein catheterization surgery. Both groups were submitted to acute stress induced by formalin (4%) subcutaneous injection or restrained stress in a PVC tube. One hour stress sessions were performed during proestrous morning. Blood samples were obtained in 2, 5, 10, 15, 30 and 60 minutes after acute or during restrained stress. Seric prolactin concentration was measured by radioimmunoassay. The results showed an increased prolactin release at 10 and 15 minutes in primiparous compared to nulliparous during restrained stress (Repeated Measures Anova, F 5,15 = 9,65; p< 0,001). No differences between groups were observed in prolactin release after formalin injection. In conclusion, we can suggest that prolactin secretory stress response can be modulated by reproductive experience although further studies are necessary to elucidate oestrus cycle and different contribution of stress types.